EFO2 promotes triple-negative breast cancer progression and reduces CD8+ T cell-mediated killing by acetylating USF1 to enhance SLC2A1-mediated glycolysis.

Abstract

Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by significant intratumoral heterogeneity and poor prognosis. Our study identified Establishment Factor-Like Protein 2 (EFO2) as a key oncogenic driver of TNBC progression. Using GEO datasets, we identified differentially expressed genes in TNBC. Functional roles of EFO2 were assessed via knockdown in human (MDA-MB-231, HCC1937) and mouse (4 T1, EMT6) TNBC cells, examining proliferation, glycolysis, and co-culture with CD8⁺ T cells. In vivo tumor growth was evaluated. Molecular mechanisms were investigated through co-immunoprecipitation, mutagenesis, luciferase reporter, and ChIP-qPCR assays. We observed that EFO2 was highly expressed in TNBC tissues, and this high expression correlated with shorter patient survival. Functional experiments showed that EFO2 knockdown suppressed tumor growth and proliferation both in vitro and in vivo. Furthermore, EFO2 knockdown inhibited glycolysis, as evidenced by decreased glucose uptake, ATP production, and lactate production. Moreover, EFO2 deficiency enhanced CD8⁺ T cell-mediated cytotoxicity against TNBC cells. Mechanistically, we demonstrated that EFO2 promoted the acetylation of Upstream Transcription Factor 1 (USF1), thereby enhancing transcriptional upregulation of the SLC2A1 promoter, a key glucose transporter. This EFO2/USF1/SLC2A1 signaling axis accelerated glycolysis in TNBC cells, which concurrently sustained tumor proliferation and impaired CD8⁺ T cell effector function, reducing TNBC cell susceptibility to T cell-mediated killing. Our findings identify a novel EFO2/USF1/SLC2A1 signaling axis that modulates glycolytic metabolism and CD8⁺T cell cytotoxicity, positioning EFO2 as a promising therapeutic target for TNBC treatment.